I heard water once flowed from Baba's feet. What's the story behind that?

This miracle is detailed in Chapter 4 and involves Das Ganu. On a special holy day, Das Ganu felt a strong desire to go to Prayag for a sacred bath in the confluence of the rivers. He went to Sai Baba to ask for permission to leave Shirdi. Baba advised him against the long journey, stating, "No need to go so far. This itself is our Prayag; keep firm faith in your mind." To demonstrate this, a wondrous event occurred. As Das Ganu bowed to touch Baba's feet, water representing the holy rivers Ganga and Yamuna began to drip from both of Baba's big toes. Witnessing this incredible leela, Das Ganu was completely overcome with emotion and devotion, realizing that the holiest of places was right there at his Guru's feet.